1. Field of Invention
The present invention relates to a liquid crystal display (LCD) panel. More particularly, the present invention relates to an optically compensated birefringence LCD panel having short response time.
2. Description of Related Art
Liquid crystal displays are divided into many categories based on the type of liquid crystal used, the driving method, and the location of light source disposition. Wherein, optically compensated birefringence liquid crystal display (OCB LCD) has very quick response speed and can provide more smooth display quality while playing fast-switching continuous images such as animations, so it is very suitable to be applied to high-scale LCD. However, the optically compensated birefringence LCD can only enter standby status to provide quick response performance after all the liquid crystal molecules are switched from splay state to bend state.
FIG. 1A is a diagram illustrating liquid crystal molecules in splay state in a LCD panel. FIG. 1B is a diagram illustrating liquid crystal molecules in bend state in a LCD panel. Referring to both FIG. 1A and FIG. 1B, in the optically compensated birefringence LCD panel 10, the liquid crystal layer 11 is disposed between the top substrate 12 and the bottom substrate 13. The top substrate 12 and the bottom substrate 13 respectively have an alignment layer (not shown) parallel to each other in the rubbing direction. The liquid crystal molecules in the liquid crystal layer 11 are arranged in splay state while they are not affected by external electric field. While the optically compensated birefringence LCD is entering standby status, an electric filed vertical to the top substrate 12 has to be applied to the liquid crystal molecules to change all the liquid crystal molecules to bend state. In the conventional optically compensated birefringence LCD, a few minutes are needed for the transition procedure to be processed if the pixels are to be driven properly, that is, long time warm up is needed before entering standby status. However, this is very disadvantageous to the “instant on” characteristic of LCD. Thus, to make the optically compensated birefringence LCD more acceptable to consumers, fast transition is necessary.
In order to have the liquid crystal molecules in the optically compensated birefringence LCD transit from splay state to bend state quickly, in a conventional technology, intense electric field is produced by applying high voltage.
FIG. 1C is a cross-sectional view of a conventional optically compensated birefringence LCD panel, and FIG. 1D is a top view of an active device array apparatus in the optically compensated birefringence LCD panel in FIG. 1C, wherein FIG. 1C is a cross-sectional view of FIG. 1D cut along line A-A′. Referring to both FIG. 1C and FIG. 1D, the optically compensated birefringence LCD panel 100 includes a thin film transistor (TFT) array apparatus 110, a color filter apparatus 120, and a liquid crystal layer 130 disposed between the TFT array apparatus 110 and the color filter apparatus 120.
The TFT array apparatus 110 includes a bottom substrate 111, a plurality of scan lines 112, a plurality of data lines 113, a plurality of thin film transistors 114, a plurality of transmissive conductive electrodes 115 (such as Indium Tin Oxide—ITO), a plurality of control signal electrodes 116, and an alignment layer 117. The scan lines 112 and the control signal electrodes 116 are all disposed on the bottom substrate 111. The data lines 113 are disposed over the control signal electrodes 116 (in other conventional technology, the control signal electrodes 116 can also be disposed over the data lines 113). The thin film transistors 114 are electrically connected to the scan lines 112 and the data lines 113 respectively. The transmissive conductive electrodes 115 are electrically connected to the thin film transistors 114 respectively. The alignment layer 117 covers the transmissive conductive electrodes 115.
The color filter apparatus 120 includes a top substrate 121, a black matrix 122, a color filter layer 123, an insulating layer 124, a common electrode 125, and an alignment layer 126. The black matrix 122 and the color filter layer 123 are both disposed on the top substrate 121. The insulating layer 124 covers the black matrix 122 and the color filter layer 123. The common electrode 125 is disposed on the insulating layer 124. The alignment layer 126 is disposed on the common electrode 125.
A high voltage is supplied to the control signal electrodes 116 before the optically compensated birefringence LCD panel 100 displays an image, so that some liquid crystal molecules close to the data lines 113 in the liquid crystal layer 130 over the control signal electrodes 116 transit from splay state to bend state. While scan signals and data signals are respectively supplied to the scan lines 112 and the data lines 113 to display image on the optically compensated birefringence LCD panel, the rest liquid crystal molecules in splay state will transit to bend state under the affection of the liquid crystal molecules which have transited to bend state. In other words, the optically compensated birefringence LCD panel 100 will represent quick response speed.
However, since the data lines 113 are close to the control signal electrodes 116 supplied with a high voltage, thus, the data signal transmission in the data lines 113 are affected by load increase, which will further induce the problem of signal delay, and meanwhile, increase the consumption power of the driver IC.